JPWO2019026251A1 - Titanium chunk, method for producing the same, and titanium slab - Google Patents

Abstract

It is a plate-shaped titanium lump having a thickness of 7 to 80 mm and a chemical composition in mass% of O: 0.01 to 0.5%, Fe: 0.01 to 5%, Al: 0 to 8%, Sn: 0 to 5%, Zr: 0 to 12%, Mo: 0 to 15%, Ta: 0 to 2%, V: 0 to 22%, Nb: 0 to 2%, Si: 0 to 1%, Cr : 0 to 10%, Cu: 0 to 0.1%, Co: 0 to 1%, Ni: 0 to 1%, platinum group element: 0 to 0.5%, REM: 0 to 0.2%, B : 0 to 3%, N: 0 to 0.2%, C: 0 to 2%, H: 0 to 0.013% The balance is titanium and impurities, the maximum value CMAX and the minimum value of the measured values of each element. The difference ΔC of CMIN is less than 0.2 CMIN or less than 0.04%, and the metal structure is such that the circle-equivalent average crystal grain size at the center in the thickness direction of the titanium lump is 10 mm or less and half or less of the thickness There, titanium mass. This titanium mass can be manufactured at low cost.

Description

  The present invention relates to a titanium ingot, a method for producing the same, and a titanium slab.

  Titanium materials are metal materials with excellent corrosion resistance, and are used in heat exchangers using seawater, various chemical plants, and the like. Titanium materials are often used in aircraft bodies because of their lower density than carbon steel and excellent specific strength (strength per unit weight). In addition, by using titanium materials for land transportation equipment such as automobiles, the equipment itself becomes lighter, and thus fuel efficiency is expected to be improved.

  However, a titanium material is more complicated than a steel material and is manufactured by a great number of processes. Typical processes include the following.

  (A) Smelting process: Production of massive and sponge metal titanium (hereinafter referred to as “sponge titanium”) by chlorination of titanium oxide as raw material to titanium tetrachloride and reduction with magnesium or sodium Process.

  (B) Melting step: A step in which sponge titanium is press-molded to form an electrode and melted in a vacuum arc melting furnace to produce an ingot.

  (C) Forging step: A step of producing a slab (hot rolled material), billet (hot extrusion, hot rolled material, etc.) by forging the ingot hot.

  (D) Hot working step: A step of heating a slab or billet and hot rolling or extruding to produce a plate or a round bar.

  (E) Cold working step: A step of producing a thin plate, round bar, wire, etc. by further cold rolling a plate or round bar.

  Titanium materials are very expensive because they are manufactured in many processes. For this reason, titanium materials are hardly applied to land transportation equipment such as automobiles. In order to promote the use of titanium materials, it is necessary to improve the productivity of the manufacturing process. As a technique for dealing with this problem, an effort to omit the manufacturing process of the titanium material has been made.

  Since VAR (vacuum arc melting) can only produce cylindrical titanium ingots, in order to perform hot rolling after this to make a thin plate, the cylindrical titanium ingot is hot forged to form a rectangular parallelepiped. Titanium, that is, titanium slab.

  On the other hand, in electron beam melting or plasma melting, melted titanium is held in a container (cold hearth) and then injected into molds of various shapes. For this reason, by using a rectangular parallelepiped mold, a direct slab-shaped titanium ingot can be obtained, and the forging process can be omitted (direct slab casting method). The melted titanium begins to solidify from the surface of the titanium ingot in contact with the mold, and eventually the thickness central portion is solidified to obtain a titanium ingot. At the same time, the titanium ingot is drawn downward from above and gradually solidifies from below to above.

  Patent Document 1 discloses an invention for manufacturing a titanium ingot by omitting a melting step. This titanium ingot (slab) is manufactured by compressing and forming porous titanium (sponge titanium) into an ingot shape and melting the surface under vacuum. The inside is porous titanium and the entire surface is dense. It is covered with special titanium. According to the invention disclosed in Patent Document 1, since a slab-shaped titanium ingot is produced using sponge titanium or a compression molded body thereof, a thin slab can be produced.

  Patent Document 2 discloses an invention in which a titanium alloy round bar is manufactured by adding copper powder, chromium powder or iron powder to a titanium alloy powder, encapsulating it in a carbon steel capsule, heating and extruding it hot. Has been. In Patent Document 3, titanium powder or titanium alloy powder containing hydrogen is filled in capsules, dehydrogenated by heating while reducing pressure, and then extruded hot to produce titanium round bars or titanium alloy round bars. The invention is disclosed. Patent Document 4 discloses an invention relating to a titanium material in which a packing material formed of a pure titanium material is filled with one or more selected from sponge titanium, titanium briquette, and titanium scrap.

Japanese Patent Laying-Open No. 2015-45040 JP 2014-019945 A JP 2012-041583 A International Publication No. 2016/056607

  The direct slab casting method is an excellent method capable of omitting the forging process, but the obtained slab thickness is 100 mm or more, and is usually about 200 mm to 400 mm. Since the thickness of the slab is determined by the thickness of the mold, the thickness of the slab can be reduced by reducing the thickness of the mold.

  However, when the thickness of the mold is less than 100 mm, when molten titanium is poured into the mold from cold hearth, the molten titanium scatters out of the mold, or the molten titanium is evenly distributed in the width direction of the mold from the injected portion. Trouble that does not flow into the.

  In addition, in order to obtain a titanium thin plate having a thickness of several millimeters or less from a slab having a thickness of 100 mm or more, a large hot processing facility is necessary because it must be subjected to a large processing. It must be processed repeatedly and is inefficient.

  Furthermore, a slab having a thickness of 100 mm or more has a slow internal cooling rate due to its thickness, and crystal grains grow very large. For this reason, in order to obtain mechanical properties such as tensile properties necessary for products, it is necessary to perform large processing to break coarse crystal grains and make them fine. Due to its thickness, solidification segregation increases, and the difference between the surface layer and the central component of the slab is large. Further, in the length (up and down) direction of the titanium ingot, the central portion of the thickness above the slab that solidifies last is particularly easily solidified and segregated, and easily segregates Fe, Cr, Co, Cu, Ni, V, and Si. Etc. thicken.

  In the direct slab casting method, since titanium dissolved in the vacuum chamber is held in the cold hearth, a part of titanium and the auxiliary material (alloy additive element) is volatilized and adheres to the wall surface of the chamber in a large amount. For this reason, the yield at the time of obtaining an ingot worsens. Moreover, since it takes time to remove the volatile matter adhering to the chamber wall surface, the workability is poor. In the case of a titanium alloy containing an element (Al, Cu, Sn, etc.) that is more volatile than titanium, the content of the volatile element in the slab is less than the content in the titanium raw material. For this reason, the amount of volatilization of each element is predicted, and a larger amount corresponding to them is added to the titanium raw material.

  However, the volatilization amount varies greatly depending on the operating conditions such as the dissolution rate, the slab drawing speed, and the EB irradiation conditions. For example, the dissolution rate varies depending on the size and shape of the titanium raw material, and when the dissolution rate decreases, the amount of molten titanium flowing through cold hearth decreases and the volatilization amount increases. The slab drawing speed decreases at the beginning and end of casting when there is less molten titanium in the cold hearth. During this time, the time for EB irradiation to the molten titanium in the mold becomes longer, and the volatilization amount increases. Irradiation conditions can be basically constant. However, when an operation trouble occurs, it is necessary to reduce or stop the output, so that the dissolution rate decreases or the dissolution stops. When the output is lowered, the volatilization amount decreases. It is extremely difficult to predict and manage these operating conditions, and for this reason, fluctuations in the components are inevitable in the longitudinal direction of the slab.

  Since the inside of the titanium ingot disclosed in Patent Document 1 is granular sponge titanium, basically, only a titanium ingot having the same chemical composition as that of sponge titanium can be obtained. In order to obtain a titanium ingot having a chemical composition different from the chemical composition of sponge titanium, necessary elements must be added. For example, in order to increase the oxygen of titanium in order to increase the strength, titanium oxide powder is added to Ti-6Al-4V alloy, and in the case of Ti-6Al-4V alloy, Al-V alloy particles or Al particles are added to sponge titanium and mixed.

  However, since there is no subsequent dissolution step, the sponge titanium and the additive element powder and particles are not easily homogenized. In order to perform a solution heat treatment after the hot working to achieve homogenization by diffusion of each element, it is necessary to perform a solution treatment for an enormous amount of time, which is not practical. For this reason, in the invention disclosed by patent document 1, only the titanium ingot which has a chemical composition equivalent to sponge titanium can be manufactured, and a titanium alloy ingot cannot be manufactured.

  Furthermore, when the as-cast surface is hot-rolled, the surface of the obtained titanium thin plate is liable to have a bald surface defect. Since the titanium ingot disclosed in Patent Document 1 is obtained by melting and solidifying only the surface thereof, the surface has a rough cast structure (coarse crystal grains). During the next hot rolling, the rough cast structure (coarse crystal grains) on the surface of the ingot is undulated on the surface of the ingot due to strong plastic anisotropy due to the difference in crystal orientation. This is because of surface defects.

  According to the inventions disclosed in Patent Documents 2 and 3, various titanium and titanium alloy round bars can be manufactured by using powder as a raw material and adding various elements as powder. This is because a powder finer than sponge titanium is used, so that a homogeneous round bar can be obtained even if the solution treatment after hot working is relatively short. However, labor and cost are required to produce raw material powders such as titanium powder, titanium alloy powder, and alloy addition powder.

  According to the invention disclosed in Patent Document 4, since the melting step and the forging step can be omitted, a titanium material can be obtained at a low cost. However, since titanium sponge and the like are used as they are, as in the invention of Patent Document 1, only a titanium ingot having a chemical composition equivalent to that of sponge titanium can be produced, and a titanium alloy ingot cannot be produced. To do.

  In view of such circumstances, the present invention is a low-cost titanium ingot for hot working or cold working, particularly a titanium ingot having various chemical compositions with a thin wall thickness or a small diameter, which is a raw material for a titanium thin plate or a titanium wire. The purpose is to manufacture with.

  As a result of intensive studies to solve the above problems, the present inventors have conceived that a titanium ingot that can omit the forging process and can further simplify the hot working process can be produced.

  FIG. 1 is an explanatory view schematically showing a titanium briquette 1.

  The raw material to be used is sponge titanium 1a, which is manufactured in a normal process and can be obtained at a relatively low cost. Even if electron beam melting is performed while the granular sponge titanium 1a is used, the shape of the titanium sponge 1a is compression-molded into a rectangular parallelepiped titanium briquette 1 as shown in FIG.

  At this time, an auxiliary material 1c containing an element (oxygen, Fe, Al, V, etc.) necessary for obtaining a titanium lump having a required chemical composition is added to and mixed with sponge titanium 1a, and then compression-molded. Obtain briquette 1.

  Since the titanium briquette 1 has a gap 1d inside, after removing the air present in the gap 1d under reduced pressure, a part (for example, approximately half) 2a in the thickness direction of the titanium briquette 1 is melted by an electron beam. To do.

  FIG. 2 is an explanatory view schematically showing the titanium block 2.

  Thereafter, the titanium briquette 1 is inverted, and the remaining part (for example, approximately half) 2b in the thickness direction that has not yet been melted is similarly melted by the electron beam. As a result of evacuation of the gap 1d and dissolution of the titanium briquette, the inventors dissolved the added auxiliary raw material 1c together with the sponge titanium 1a and became homogeneous. As shown in FIG. It was found that it was obtained.

  At this time, in order to prevent bubbles from remaining inside the titanium lump 2, the air present in the gaps 1d between the titanium sponge 1a grains must be sufficiently removed. It has also been found that it is important to place the titanium briquette 1 before melting the electron beam in an atmosphere where the pressure is reduced as much as possible.

  In order to melt and solidify a part of the titanium briquette 1 with an electron beam, and since the thickness of the titanium lump 2 is thin, all the raw materials are injected into the mold after melting and solidified and cooled as in the conventional melting process. The inventors have also found that the cooling rate after solidification is faster than that of a titanium material having a large thickness, and the crystal grains inside the titanium block 2 do not become coarse.

  Further, the titanium sponge 1a is compression-molded into a cylindrical, prismatic or polygonal rod shape to form a titanium briquette 1, and similarly, by melting with an electron beam, a cylindrical, prismatic or polygonal columnar rod shape is obtained. It has also been found that a small-diameter titanium block 2 can be obtained.

  FIG. 4 is an explanatory view schematically showing the titanium slab 3.

  Furthermore, in order to suppress surface defects during hot working, the titanium block 2 obtained above is filled in a container (packing material) 4 made of a titanium plate 4a having the same chemical composition, and the packing material All the joints of 4 were welded to form a welded portion 5 to obtain a titanium slab 3 shown in FIG. The inventors have also found that this titanium slab 3 can be used as a titanium material for hot working.

  The present invention is based on these novel findings and is listed below.

(1) A plate-like titanium block having a thickness of 7 to 80 mm,
Chemical composition is mass%,
O: 0.01 to 0.5%
Fe: 0.01 to 5%,
Al: 0 to 8%,
Sn: 0 to 5%
Zr: 0 to 12%,
Mo: 0 to 15%,
Ta: 0 to 2%
V: 0 to 22%
Nb: 0 to 2%,
Si: 0 to 1%,
Cr: 0 to 10%
Cu: 0 to 0.1%,
Co: 0 to 1%,
Ni: 0 to 1%,
Platinum group elements: 0 to 0.5%,
REM: 0-0.2%
B: 0 to 3%
N: 0 to 0.2%,
C: 0 to 2%
H: 0 to 0.013%
The balance is titanium and impurities,
The difference ΔC between the maximum value C _MAX and the minimum value C _MIN of the measured values of each element is less than 0.2C _MIN or less than 0.04%,
The metal structure is
The circle-equivalent average crystal grain size in the central portion of the titanium lump in the thickness direction is 10 mm or less and half or less of the thickness of the titanium lump.
Titanium lump.

(2) A titanium lump having a columnar shape in which the cross section perpendicular to the longitudinal direction is a circle having a diameter of 10 to 80 mm, or a columnar shape that is a pentagon or more polygon having a circle equivalent diameter of 10 to 80 mm,
Chemical composition is mass%,
O: 0.01 to 0.5%
Fe: 0.01 to 5%,
Al: 0 to 8%,
Sn: 0 to 5%
Zr: 0 to 12%,
Mo: 0 to 15%,
Ta: 0 to 2%
V: 0 to 22%
Nb: 0 to 2%,
Si: 0 to 1%,
Cr: 0 to 10%
Cu: 0 to 0.1%,
Co: 0 to 1%,
Ni: 0 to 1%,
Platinum group elements: 0 to 0.5%,
REM: 0-0.2%
B: 0 to 3%
N: 0 to 0.2%,
C: 0 to 2%
H: 0 to 0.013%,
The balance is titanium and impurities,
The difference ΔC between the maximum value C _MAX and the minimum value C _MIN of the measured values of each element is less than 0.2C _MIN or less than 0.04%,
The metal structure is
In a cross section perpendicular to the longitudinal direction of the titanium block, it has a columnar structure extending in the direction from the surface toward the center, the circle-equivalent average crystal grain size at the center position of the cross section is 10 mm or less, and half or less of the diameter of the cross section Is,
Titanium lump.

(3) a packing material having the same chemical composition as the titanium block of (1) or (2) above,
The above-mentioned (1) or (2) titanium ingot filled in the packing material,
The packing material has an internal pressure of 10 Pa or less,
Titanium slab.

(4) a compression molding step of obtaining a titanium briquette by compression molding one or more selected from sponge titanium and titanium scrap and an auxiliary material containing an element necessary for adjusting the chemical composition;
A step of irradiating the surface of the titanium briquette with an electron beam under a reduced pressure of 1 Pa or less to dissolve all of the titanium briquette into a titanium lump,
The manufacturing method of the titanium lump of said (1) or (2).

(5) The melting step irradiates an arbitrary surface of the titanium briquette with an electron beam, melts a part of the thickness direction from the surface, and irradiates an electron beam with any other surface, Dissolving at least undissolved titanium briquettes,
The manufacturing method of the titanium lump of said (4).

ADVANTAGE OF THE INVENTION According to this invention, it is a raw material which can be used for manufacturing a titanium thin plate or a titanium wire by hot processing or cold processing, Comprising: The titanium lump which has various chemical compositions can be manufactured at low cost.
The titanium ingot according to the present invention is a thin or small-diameter slab (square column (for example, plate-like), cylinder, polygonal column), and the processing rate when manufacturing titanium thin plates and rods can be reduced. Titanium thin plates and rods can be manufactured efficiently and inexpensively.
Since the titanium lump of the present invention is a thin-walled plate-like or small-diameter columnar titanium lump, the thickness center part (plate-like titanium lump) or the center part in the cross section perpendicular to the longitudinal direction (columnar titanium lump) The crystal grains are small and solidification segregation is small.
A titanium slab in which a packing material made of a titanium plate is filled with the titanium block according to the present invention can suppress the occurrence of surface defects during hot working.
According to the production method of the present invention, it is possible to stably obtain a titanium ingot having a target component by simply adjusting the electron beam irradiation condition to be constant.

FIG. 1 is an explanatory view schematically showing an example of a titanium briquette. FIG. 2 is an explanatory view schematically showing an example of a titanium block. FIG. 3 is an explanatory view schematically showing another example of a titanium block. FIG. 4 is an explanatory view schematically showing an example of a titanium slab. FIG. 5 is an explanatory view schematically showing another example of a titanium slab. FIG. 6 is a schematic diagram showing a sample for analysis.

  The raw material, titanium briquette, titanium lump, and titanium slab used in the present invention will be described in order with reference to the attached drawings. In the following description, “%” regarding chemical composition means “% by mass” unless otherwise specified.

  FIG. 1 is an explanatory view schematically showing a titanium briquette 1, FIG. 2 is an explanatory view schematically showing a titanium lump 2, and FIGS. 4 and 5 are schematic views of titanium slabs 3 and 30. It is explanatory drawing shown.

  As shown in FIG. 1, the titanium briquette 1 includes one or more of sponge titanium 1a and titanium scrap 1b and elements necessary for achieving the function as the final product (for example, oxygen, Fe, Al, V, etc.). The auxiliary raw material 1c is mixed and obtained, for example, by compression molding into a rectangular parallelepiped shape.

1. The raw material of the titanium briquette 1 First, the raw material of the titanium briquette 1 is demonstrated. The raw material of the titanium briquette 1 includes at least one of sponge titanium 1a and titanium scrap 1b, and includes auxiliary raw materials 1c that selectively contain various elements.

(1-1) Size of Sponge Titanium When titanium sponge 1a is used as a raw material for titanium briquette 1, one produced by a refining process such as a conventional crawl method can be used. Since the sponge titanium 1a obtained in this smelting process is a large lump usually having several tons, it is desirable to use a crushed and granulated product as in the conventional process.

  The average size of the sponge titanium 1a is 1 mm or more and 25 mm or less (however, when used for a plate-like titanium lump, less than the thickness of the titanium lump, when used for a polygonal columnar or cylindrical titanium lump, titanium Desirably less than the diameter of the lump). If the average particle size is less than 1 mm, it takes time to crush, and a lot of fine dust is scattered, resulting in a reduction in production efficiency. On the other hand, if the average particle size is larger than 25 mm, there is a limit to the range in which the titanium briquette 1 can be dissolved by irradiating an electron beam in a subsequent process, and thus there is a possibility that the auxiliary raw material 1c cannot be dissolved uniformly.

(1-2) Chemical composition of sponge titanium The sponge titanium 1a is a raw material of the titanium lump 2, and contains oxygen, iron, nitrogen, carbon, hydrogen, chlorine, magnesium and the like in addition to titanium. Specifically, oxygen 0.40% or less, iron 0.50% or less, nitrogen 0.05% or less, carbon 0.08% or less, hydrogen 0.013% or less, chlorine 0.10% or less, magnesium 0. 10% or less is exemplified.

  These amounts are preferably equal to or less than those required for the titanium block 2. If the amount of elements other than titanium contained in the sponge titanium 1a is equivalent to the amount required for the titanium lump 2, the sponge titanium 1a can be used as it is. If the amount of elements other than titanium contained in the sponge titanium 1a is smaller than the amount of elements other than titanium required for the titanium mass 2, it can be compensated by adding the auxiliary raw material 1c in an amount necessary for its chemical composition. Good.

  If the amount of elements other than titanium contained in the sponge titanium 1a is larger than the amount of elements other than titanium required for the titanium lump 2, and the amount of sponge titanium 1a is less than the amount required for the titanium lump 2, other than titanium The elements other than titanium are diluted by appropriately mixing with other sponge titanium having a small amount of element. Thereby, the target titanium lump 2 can be obtained. However, when the amount of elements other than titanium in the sponge titanium 1a is too large, it cannot be used because it cannot be diluted.

  Next, the titanium scrap 1b that can be used as a raw material will be described.

  Titanium scrap 1b is a scrap that does not become a product generated in the manufacturing process of titanium material, titanium chips generated when cutting or grinding to make the titanium material into a product shape, unnecessary after use as a product Such as titanium material.

(1-3) Size of Titanium Scrap The size of titanium scrap 1b is 1 mm or more and 25 mm or less in average particle diameter as in the case of sponge titanium 1a (however, when used for a plate-like titanium lump, the thickness of titanium lump) Or less, when used for a polygonal columnar or cylindrical titanium lump, it is desirable that the diameter be equal to or less than the diameter of the titanium lump. If the average particle size is less than 1 mm, it takes time to crush, and a lot of fine dust is scattered, resulting in a reduction in production efficiency. On the other hand, if the average particle size is larger than 25 mm, there is a limit to the range in which the titanium briquette 1 can be dissolved by irradiating the electron beam in the subsequent process, and thus there is a possibility that the added auxiliary material 1c cannot be uniformly dissolved.

  The titanium scrap 1b may be filled in the mold as it is, but titanium chips having a small bulk specific gravity are compressed in advance to increase the bulk specific gravity in order to fill more efficiently or more. Or after mixing with sponge titanium 1a.

(1-4) Chemical composition of titanium scrap When titanium scrap 1b is mixed with sponge titanium 1a, JIS type 1, JIS type 2, JIS type 3 or JIS type 4 (JIS H 4600 (2012) titanium of the same type as the titanium sponge 1a. And a titanium alloy-plate and strip). The titanium scrap 1b may be of the same type as the target chemical composition of the titanium lump 2. Here, having the same chemical composition means specifically belonging to the same JIS standard. For example, when the chemical composition of the sponge titanium 1a belongs to JIS class 1, the titanium scrap 1b to be mixed may also have a chemical composition belonging to JIS class 1. Alternatively, when it is desired to obtain a titanium block 2 having a chemical composition belonging to JIS class 2, even if the sponge titanium 1a has a chemical composition belonging to JIS class 1, the titanium scrap 1b may have a chemical composition belonging to JIS class 2. Other chemical compositions may be used, and the insufficient oxygen and iron may be adjusted by adding the auxiliary material 1c.

  Next, the auxiliary raw material 1c that can be used as the raw material will be described.

  The auxiliary material 1c is added to at least one of the titanium sponge 1a and the titanium scrap 1b in order to obtain a titanium block 2 having a target chemical composition. For example, titanium oxide is added when oxygen is added, electrolytic iron particles are added when iron is added, Al particles are added when Al is added, and Al—V alloy particles are added when Fe and Al are added. When it is desired to increase Mo, an Fe—Mo alloy is added as an auxiliary material 1c. Only one type of auxiliary material 1c may be added, or a plurality of types may be added simultaneously.

(1-5) Size of auxiliary material The size of the auxiliary material 1c is desirably a powder or a granule having an average particle diameter of 0.1 μm or more and 10 mm or less. When the average particle size is less than 0.1 μm, when such fine powder is conveyed or mixed, it easily rises and scatters to the surroundings, so that a predetermined mass cannot be added.

  On the other hand, if the average particle size is larger than 10 mm, the range in which the titanium briquette 1 can be dissolved by irradiating the electron beam in the subsequent process is limited, so that it cannot be uniformly dissolved with the sponge titanium 1a and titanium scrap 1b. Absent.

2. Titanium lump As shown in FIG. 2, the titanium lump 2 is formed by compression-molding sponge titanium 1 a into a cylindrical, prismatic or polygonal rod shape to form titanium briquette 1, and then dissolving the surface thereof. Columnar structures 2a and 2b are provided on the surface. As will be described later, the titanium block 2 is filled in a container (packing material) made of a titanium plate material, and becomes a material for forming the titanium slab 3. Alternatively, the titanium block 2 can be used as a material for hot working (intermediate product). In this case, the titanium block 2 is also referred to as a titanium slab, a titanium billet, or a titanium bloom depending on its size and shape.

(2-1) Chemical composition of the titanium lump The chemical composition of the titanium lump 2 is that of the titanium titanium 1a and / or titanium scrap 1b used as a raw material for the titanium briquette 1, its weight ratio, and the auxiliary raw material 1c to be added. Depends on chemical composition and weight percentage. Therefore, in order to obtain the target chemical composition of the titanium lump 2, the chemical composition of the sponge titanium 1a, the titanium scrap 1b, and the auxiliary raw material 1c is grasped in advance by chemical analysis or the like, and according to the chemical composition. Determine the weight of each raw material required. Note that elements that are volatilized and removed by electron beam melting (for example, chlorine and magnesium) are not included in the titanium block 2 even though they are included in the titanium briquette 1.

  The chemical composition of the titanium ingot of the present invention is mass%, O: 0.01 to 0.5%, Fe: 0.01 to 5%, Al: 0 to 8%, Sn: 0 to 5%, Zr: 0 to 12%, Mo: 0 to 15%, Ta: 0 to 2%, V: 0 to 22%, Nb: 0 to 2%, Si: 0 to 1%, Cr: 0 to 10%, Cu: 0 -0.1%, Co: 0 to 1%, Ni: 0 to 1%, Platinum group element: 0 to 0.5%, REM: 0 to 0.2%, B: 0 to 3%, N: 0 -0.2%, C: 0-2%, H: 0-0.013%, the balance being titanium and impurities.

  Specifically, the platinum group element is at least one selected from Ru, Rh, Pd, Os, Ir, and Pt, and the content of the platinum group element means the total content of the above elements. REM is a general term for a total of 17 elements of Sc, Y and lanthanoid, and the content of REM means the total amount of the above elements.

  The content of the remaining titanium in the titanium ingot is preferably 70% or more. As needed, it is good also as 75% or more, 80% or more, and 85% or more. The inclusion of Al, Sn, Zr, Mo, Ta, V, Nb, Si, Cr, Co, Ni, platinum group elements, REM, and B is not essential, and the lower limit of each content is 0%. If necessary, the lower limit of each content of Al, Sn, Zr, Mo, Ta, V, Nb, Si, Cr, Co, Ni, platinum group elements, REM, and B is 0.01%. %, 0.05%, 0.1%, 0.2%, or 0.5%.

The upper limit of O may be 0.4%, 0.3%, 0.2%, or 0.1%. The upper limit of Fe may be 3%, 2%, 1%, or 0.5%. The upper limit of the Al content may be 5%, 3%, 2%, or 1%. The upper limit of the Sn content may be 3%, 2%, 1%, or 0.5%. The upper limit of the Zr content may be 10%, 8%, 5%, or 2%. The upper limit of the Mo content may be 12%, 9%, 4%, or 2%. The upper limit of the Ta content may be 1%, 0.5%, 0.2%, or 0.1%. The upper limit of the V content may be 18%, 15%, 10%, or 5%. The upper limit of the Nb content may be 1%, 0.5%, 0.2%, or 0.1%. The upper limit of the Si content may be 0.8%, 0.5%, 0.2%, or 0.1%. The upper limit of the Cr content may be 8%, 5%, 2%, or 1%. The upper limit of the Co content may be 0.8%, 0.5%, 0.2%, or 0.1%. The upper limit of the Ni content may be 0.8%, 0.5%, 0.2%, or 0.1%. The upper limit of the platinum group element content may be 0.4%, 0.3%, 0.2%, or 0.1%. The upper limit of N may be 0.1%, 0.05%, 0.03%, or 0.02%. The upper limit of Cu may be 0.8%, 0.5%, 0.2%, or 0.1%. The upper limit of C may be 1%, 0.5%, 0.2%, or 0.1%. The upper limit of the REM content may be 0.1%, 0.05%, 0.03%, or 0.02%. The upper limit of the B content may be 2%, 1%, 0.5%, or 0.3%.
The purpose of adding each element is shown in Table 1.

  The titanium block 2 is preferably manufactured so as to satisfy the chemical composition range defined in various standards. Although there are ASTM standards and AMS standards, the following are mainly exemplified JIS standards as typical standards. The present invention can be used to produce titanium or titanium alloys of these standards.

(2-1-1) Industrial Pure Titanium Industrial Pure Titanium belongs to JIS Class 1 to JIS Class 4 (JIS H 4600 (2012) Titanium and Titanium Alloy-Plate and Strip) with oxygen and Fe adjusted. Illustrative is titanium. The industrial pure titanium has better workability as the amount of oxygen and Fe decreases, and the strength increases as the amount of oxygen and Fe increases. JIS type 1 is C: 0.08% or less, H: 0.013% or less, O: 0.15% or less, N: 0.03% or less, Fe: 0.20% or less, the balance of Ti and impurities Titanium having a chemical composition. JIS type 2 is C: 0.08% or less, H: 0.013% or less, O: 0.20% or less, N: 0.03% or less, Fe: 0.25% or less, the balance of Ti and impurities Titanium having a chemical composition. JIS class 3 means C: 0.08% or less, H: 0.014% or less, O: 0.30% or less, N: 0.05% or less, Fe: 0.30% or less, the balance of Ti and impurities Titanium having a chemical composition. JIS class 4 is C: 0.08% or less, H: 0.015% or less, O: 0.40% or less, N: 0.05% or less, Fe: 0.50% or less, the balance of Ti and impurities Titanium having a chemical composition.

(2-1-2) Corrosion-resistant titanium alloy Corrosion-resistant titanium alloys are titanium belonging to JIS class 11 to JIS class 23 (JIS H 4600 (2012) titanium and titanium alloys-plates and strips) including Pd, Ru, Ni, Co and the like. Illustrated in alloys. The corrosion resistant titanium alloy is excellent in corrosion resistance and crevice corrosion resistance.

(2-1-3) Titanium alloy Titanium alloy is Ti-1.5Al ((JIS 50 class (JIS H 4600 (2012) titanium and titanium alloy-plate and strip)), Ti-6Al-4V (JIS 60 class ( JIS H 4600 (2012) titanium and titanium alloy-plate and strip)), Ti-3Al-2.5V (JIS 61 class (JIS H 4600 (2012) titanium and titanium alloy-plate and strip)), Ti-4Al -22V (JIS 80 type (JIS H 4600 (2012) titanium and titanium alloy-plate and strip)) and the like.

  Ti-1.5Al is excellent in corrosion resistance and excellent in hydrogen absorption resistance and heat resistance.

  Ti-6Al-4V has high strength and high versatility.

  Ti-3Al-2.5V has good weldability and formability and good machinability.

  Ti-4Al-22V has high strength and excellent cold workability.

  According to this invention, the titanium lump 2 which has a chemical composition not prescribed | regulated to JIS other than the above can also be manufactured. For example, as listed below.

Ti-6Al-2Sn-4Zr-2Mo-0.08Si having heat resistance, Ti-6Al-5Zr-0.5Mo-0.2Si, Ti-8Al-1Mo-1V, etc.
Low alloy and high strength Ti-1 to 1.5Fe-0.3 to 0.5O-0.01 to 0.04N and the like, Ti-6Al-2Sn-4Zr-6Mo and the like excellent in creep resistance,
Ti-15V-3Cr-3Sn-3Al, Ti-20V-4Al-1Sn, etc. with high strength and good cold workability,
High strength and high toughness Ti-10V-2Fe-3Al, etc.
Abrasion resistance Ti-6Al-4V-10Cr-1.3C etc. are illustrated.

(2-2) Shape of titanium block The shape of the titanium block 2 is preferably a plate shape or a column shape. The thickness of the plate-like titanium block 2 is 7 to 80 mm. The upper limit of the thickness may be 70 mm, 60 mm, 50 mm, or 40 mm. The columnar titanium block 2 may have a circular shape in a cross section perpendicular to the longitudinal direction or a polygon that is a pentagon or more. When the cross-sectional shape is circular, the cross-sectional diameter is 10 to 80 mm. The upper limit of the cross-sectional diameter may be 70 mm, 60 mm, 50 mm, or 40 mm. In the case of a polygon, the circle equivalent diameter is 10 to 80 mm. The upper limit of the equivalent circle diameter may be 70 mm, 60 mm, 50 mm, or 40 mm. The equivalent circle diameter is the diameter of a circle corresponding to the cross-sectional area.

  The width of the plate-like titanium block 2 need not be specified. However, the lower limit may be equal to the thickness or 100 mm. The upper limit may be 100 mm, 500 mm, 1000 mm, or 2000 mm. The length of the titanium block 2 need not be specified. However, the lower limit may be equal to the plate width, diameter, or equivalent circle diameter, or 100 mm. The upper limit may be 500 mm, 1000 mm, 3000 mm, 5000 mm, or 10000 mm.

  Since the titanium briquette 1 has a gap 1 d, the volume of the titanium block 2 made from the titanium briquette 1 is smaller than that of the titanium briquette 1. For this reason, in order to obtain the titanium block 2 having a desired size, it is necessary to determine the size of the titanium briquette 1 in consideration of the bulk specific gravity of the titanium briquette 1.

  For example, in order to obtain a rectangular parallelepiped titanium lump 2 (bulk specific gravity 4.5) having a thickness of 50 mm, a rectangular parallelepiped titanium briquette 1 (bulk specific gravity 3.2) having a thickness of 70 mm may be prepared. Further, in order to obtain a columnar titanium block 2 (bulk specific gravity 4.5) having a diameter of 50 mm, a columnar titanium briquette 1 (bulk specific gravity 3.1) having a diameter of 60 mm may be prepared.

  When the titanium block 2 is plate-shaped, if the thickness is less than 7 mm, the thickness of the titanium briquette 1 is thin and the strength is reduced. In this case, when the titanium briquette 1 is handled, such as moving or reversing, it breaks or corners are missing. On the other hand, if the thickness is larger than 80 mm, it is necessary to increase the dissolution depth of the titanium briquette 1 in the titanium lump manufacturing process described later. In this case, the cooling rate after dissolution becomes slow and the crystal grains become coarse. In addition, a huge output electron beam is required as in the conventional melting step.

  When the titanium block 2 has a column shape, the diameter (equivalent circle diameter in the case of a polygonal column shape) is less than 10 mm, the diameter of the titanium briquette 1 is also small and the strength is small. In this case, the titanium briquette 1 is broken or broken when it is moved or rotated. On the other hand, when the diameter (equivalent circle diameter in the case of a polygonal column shape) is larger than 80 mm, it is necessary to increase the dissolution depth of the titanium briquette 1 in the titanium lump manufacturing process described later. In this case, the subsequent cooling rate becomes slow and the crystal grains become coarse. In addition, a huge output electron beam is required as in the conventional melting step.

(2-3) Size of crystal grain of titanium lump When the titanium lump 2 is plate-shaped and the thickness is 7 to 80 mm, as shown in FIG. Columnar structures 2a and 2b extending in the thickness direction from the surface of the film. The central portion of the titanium block 2 in the plate width direction and the longitudinal direction and the central portion in the thickness direction (the region indicated by the symbol A in FIG. 2, hereinafter referred to as the central region. The central region is the central portion in the plate thickness direction. The average equivalent crystal grain size in circle is 10 mm or less and half or less of the thickness of the titanium block 2. The titanium block 2 is a circular cylinder having a diameter of 10 to 80 mm, or a polygon having a pentagon or more, and an equivalent circle diameter (diameter of a circle whose cross-sectional area is the same as the cross-sectional area of the polygon) is 10 to 10. In the case of having a polygonal column shape of 80 mm, as shown in FIG. 3, in a cross section perpendicular to the longitudinal direction of the titanium block 2, a columnar structure 30 a extending in the direction (radial direction) from the surface toward the center is obtained. The circle-equivalent average crystal grain size is 10 mm or less at the central portion in the longitudinal direction and at the center position of the cross section (the region indicated by symbol C in the figure, hereinafter referred to as the central region), and half the cross sectional diameter of the titanium block 2 It is as follows. Thereby, even if it is a small processing rate when carrying out hot processing of the titanium lump 2, a crystal grain can be parted easily and it can be made into the fine grain required for a product.

  The titanium block melted by irradiating the surface of the titanium briquette with an electron beam is quickly solidified and rapidly cooled from the surface when the irradiation is stopped. For this reason, in the cross section perpendicular to the longitudinal direction of the titanium block 2, the crystal grains extend from the surface in a columnar shape toward the direction perpendicular to the surface. Since the thickness of the titanium ingot (plate shape) is as thin as 7 to 80 mm as compared with the conventional ingot (usually 200 to 400 mm), the central region of the titanium ingot is also quickly cooled. For this reason, the average crystal grain in the central region has a circle equivalent diameter of 10 mm or less and half or less of the thickness. Similarly, since the diameter of the titanium ingot (columnar shape) is as short as 7 to 80 mm as compared with the conventional ingot, the central region of the titanium ingot is rapidly cooled. Thereby, even if it is a small processing rate when carrying out hot processing of the titanium lump 2, a crystal grain can be parted easily and it can be made into the fine grain required for a product.

  In FIG. 2, the lengths of the columnar structures extending from the front surface side and the back surface side are substantially the same. In other words, the lengths of the crystals extending in a columnar shape from the front side and the back side are substantially the same. However, the length of the columnar structure from the front side and the length of the columnar structure from the back side may be changed by greatly changing the output of the electron beam irradiated from the front side and the back side. Even in this case, since the cooling rate near the center of the plate thickness is fast, the average crystal grain in the center region is 10 mm or less in terms of the equivalent circle diameter and half or less of the thickness. In FIG. 3, the lengths of the columnar structures extending from the cylindrical surface are the same, but the lengths are not necessarily the same. Also in this case, since the cooling rate in the vicinity of the central region is fast, the average crystal grains in the central region of the cylinder are 10 mm or less in terms of the equivalent circle diameter and half or less of the diameter. In FIG. 2, as a result of irradiating the side surface with the electron beam in the plate width direction, a columnar structure having a short length extends from the side surface in the plate width direction. Although irradiation of the electron beam to such a side surface is preferable, as long as all the titanium briquettes 1 can be dissolved, irradiation of the electron beam to the side surface is not essential.

  The lower limit of the equivalent circle diameter of the average crystal grain is not particularly defined, but in order to reduce the crystal grain size in the titanium lump 2, it is necessary to extremely reduce the thickness of the titanium lump 2. However, since it is limited to the thickness of the titanium block 2 that can be manufactured, it is preferably 0.5 mm or more.

  The target crystal grains here are α-phase crystal grains in the case of industrial pure titanium and α-type titanium alloys, and β-phase crystal grains in the case of α + β two-phase titanium alloys and β-type titanium alloys. The crystal grains can be observed visually or magnified with a loupe (magnifying glass) when the cross section perpendicular to the longitudinal direction of the titanium block 2 is polished and then etched with hydrofluoric acid. Observe the crystal in the central region of the titanium ingot (region located 1/2 the thickness from the surface) to obtain the number of crystal grains, divide the observation area by the number of crystal grains, The average crystal grain is calculated by calculating the area and calculating the equivalent circle diameter. A circle is drawn in a region where 100 to 200 crystal grains are observed, the area of the circle is defined as “observation area”, and the number of crystal grains observed in the circle is defined as “number of crystal grains”. When the average crystal grain size is small and difficult to observe visually, the photomicrograph may be taken by observing with an optical microscope, and the average crystal grain may be similarly determined from the structure photograph.

In addition, in the titanium lump 2, the whole titanium briquette is finally melted and solidified by melting and sequentially solidifying a part of the titanium briquette with an electron beam. Since the range to melt | dissolve is limited to the part irradiated with the electron beam, the quantity of the titanium lump (titanium briquette) which melt | dissolves is slight. For this reason, there is little concentration of elements other than titanium at the time of solidification, that is, solidification segregation is also small. For this reason, the fluctuation | variation by the location of the component of elements other than the added titanium is also suppressed small. In addition, since titanium briquettes that are uniformly mixed in advance are partially dissolved sequentially, there is no unevenness in the dissolution of the titanium raw material, and even if there is a problem that the electron beam irradiation stops, there is no problem if it is dissolved again from that position. Does not occur. Thus, fluctuations in the longitudinal component of the slab as in the direct slab casting method can be suppressed. That is, there are few component fluctuations in the longitudinal direction of the titanium block 2, and the chemical composition thereof is uniform.

The component analysis of the titanium block 2 was performed by taking a required amount of a sample for analysis from a predetermined position of the titanium block 2 and using any of the analysis methods listed below.
JIS H 1612 (1993) Method for determination of nitrogen in titanium and titanium alloys
JIS H 1614 (1995) Determination of iron in titanium and titanium alloys
JIS H 1617 (1995) Determination of carbon in titanium and titanium alloys
JIS H 1619 (2012) Titanium and titanium alloys-Determination of hydrogen
JIS H 1620 (1995) Determination of oxygen in titanium and titanium alloys
JIS H 1621 (1992) Determination of palladium in titanium alloys
JIS H 1622 (1998) Titanium alloy-aluminum determination method
JIS H 1624 (2005) Titanium alloy-vanadium determination method
JIS H 1625 (2005) Titanium alloy-Determination of lanthanum, cerium, praseodymium and neodymium
JIS H 1630 (1995) Titanium emission spectroscopy method
JIS H 1631 (2008) Titanium alloy-X-ray fluorescence analysis method
JIS H 1632 (2014) ICP emission spectroscopic analysis method for titanium

  FIG. 6 is a schematic diagram showing a sample for analysis. As shown in FIG. 6, the sample for analysis is divided into two equal portions of 50 mm each from the front end and rear end in the longitudinal direction of the titanium block 2 (end region), and the interval between them is divided into three equal parts. The samples were collected from a total of 5 locations, 3 locations in the middle of the length. In the cross section of the titanium lump 2, in the case of a rectangular parallelepiped (slab) titanium lump 2, the center of the cross section is symmetrical in the case of a columnar (ingot) titanium lump in the surface layer on the front and back surfaces at the center in the width direction. Collected from two surface layers. Further, at a position of 50 mm from the front end and the rear end in the longitudinal direction, the sample was also taken from the center of the thickness center / diameter direction. In this way, samples for analysis were collected from a total of 12 locations (positions marked with ● in FIG. 6) and analyzed, and the uniformity of the chemical composition was evaluated as follows.

When the difference ΔC between the maximum value C _MAX and the minimum value C _MIN of the content of each element is less than 0.2C _MIN or less than 0.04%, it is evaluated as being uniform. For example, when the minimum value of the measured value of O is 0.04% and the maximum value is 0.05%, the difference ΔC (= 0.01%) is less than 0.04%, so that it is uniform. Be evaluated. Further, when the minimum value of the measured value of O is 0.30% and the maximum value is 0.32%, the difference ΔC (= 0.02%) is less than 0.2C _MIN (= 0.060%). Therefore, it is evaluated as uniform. For example, when the minimum value of the measured value of O is 0.03% and the maximum value is 0.05%, the difference ΔC (= 0.02%) is less than 0.04%, so that it is uniform. Be evaluated. When the minimum value of the measured value of O is 0.30% and the maximum value is 0.35%, the difference ΔC (= 0.05%) is less than 0.2C _MIN (= 0.060%). Therefore, it is evaluated as uniform.

3. Production Method of Titanium Briquette Titanium briquette 1 is a molded body produced by compression molding the raw materials 1a and 1b and the auxiliary raw material 1c as shown in FIG.

  Since the sponge titanium 1a and the titanium scrap 1b are indefinite, they cannot be formed into a predetermined shape (a rectangular parallelepiped, a prism, a cylinder, or the like) as they are. First, necessary titanium sponge 1a, titanium scrap 1b and auxiliary raw material 1c are put in a container and mixed. Since elements that are more volatile than titanium are volatilized and reduced by subsequent electron beam irradiation, it is preferable to add an element in an amount in consideration of the volatilization amount in advance.

  The mixed raw material is put into a die having the same shape as the cross section of the titanium briquette 1 having a desired size, and is compressed by a predetermined pressure, whereby the titanium briquette 1 is obtained. The atmosphere at the time of compression molding is usually ambient air (air).

  The mixing means is not particularly limited, but it is desirable to adopt the means described below from the viewpoint of productivity and the like.

  (A) A predetermined amount of sponge titanium 1a, titanium scrap 1b and auxiliary raw material 1c are put into a mixing container.

  (B) Agitation is performed so that the sponge titanium 1a, titanium scrap 1b, and auxiliary material 1c are uniformly mixed in the mixing container. Stirring can be performed by rotating the mixing container up and down, tilting it at an angle of 20 to 70 ° from the horizontal and rotating it in an oblique direction, vibrating the mixing container up and down, horizontally, etc. Or the like, and the stirring bar is rotated.

  (C) The stirring time is 1 to 30 minutes, depending on the size of the mixing container and the amount of the sponge titanium 1a, titanium scrap 1b and auxiliary raw material 1c to be mixed. In consideration of productivity, it is desirable to determine the size and the processing amount of the mixing container so that uniform mixing can be performed within a few minutes.

  (D) The mixed sponge titanium 1a, titanium scrap 1b, and auxiliary raw material 1c are put into a press mold for compression molding from a mixing container to perform compression molding. Thereby, the sponge titanium briquette 1 in which the auxiliary material 1c is uniformly dispersed is obtained.

  What is necessary is just to determine the magnitude | size of the titanium briquette 1 suitably according to the magnitude | size of the titanium lump 2, and the magnitude | size of the metal mold | die restricted by a compression processing apparatus.

4). Method for Producing Titanium Mass 2 Titanium mass 2 according to the present invention is obtained from titanium briquette 1 produced as described above, as shown in FIG.

(4-1) Atmosphere The titanium briquette 1 is stored in a chamber and the pressure in the chamber is reduced to 1 Pa or less. Inside the titanium briquette 1, there are many voids 1d containing air (oxygen or nitrogen). If dissolved as it is, the titanium mass 2 is oxidized, nitrided, or bubbles remain, and cracks and surfaces after hot working Causes wrinkles. For this reason, it decompresses so that it may become 1 Pa or less, and excludes air from the space | gap 1d inside the titanium briquette 1. FIG.

Although the lower limit of the pressure is not particularly limited, in order to extremely reduce the pressure in the chamber, the manufacturing cost increases by improving the airtightness of the apparatus or strengthening the vacuum evacuation equipment. The lower limit of the pressure is desirably 1 × 10 ⁻³ Pa.

(4-2) Dissolution The titanium briquette 1 installed in the decompressed chamber is first irradiated with an electron beam on the upper surface, and is sequentially dissolved and solidified. Specifically, a part (for example, approximately half) 2a in the thickness direction of the titanium briquette 1 is irradiated with an electron beam to be sequentially melted and solidified. Since the range that can be melted by the electron beam is limited, the thickness of the titanium briquette 1 is changed by moving the irradiation direction of the electron beam or moving the titanium briquette 1 to irradiate the entire upper surface of the titanium briquette 1 with the electron beam. A portion 2a in the vertical direction is dissolved and solidified.

  Thereafter, the titanium briquette 1 is inverted, and the other surface (side surface, end surface or back surface) is turned upward, and the remaining part (for example, approximately half) 2b in the thickness direction that has not been dissolved and solidified is similarly By irradiating with an electron beam, the entire region in the thickness direction of the titanium briquette 1 is sequentially melted and solidified to form a titanium lump. Thereby, a columnar structure extending in the thickness direction from the surface is obtained. In the case of the cylindrical titanium briquette 1 shown in FIG. 3, when melting the circumferential surface, the electron beam is irradiated while rotating around the axis of the cylinder, and the titanium mass is very good. Thereby, in the cross section perpendicular to the longitudinal direction of the titanium block, a columnar structure extending in the direction (radial direction) from the surface toward the center is obtained. Thus, by rotating the titanium briquette during melting (inversion of the plate briquette, rotation of the cylindrical briquette), it is possible to dissolve and solidify all of the titanium briquette to form a titanium lump.

  When the part 2a in the thickness direction of the titanium briquette 1 is melted, the electron beam is adjusted so as not to melt the entire thickness direction and the entire radial direction of the titanium briquette 1. When the entire thickness or the entire radial direction is melted (so-called electron beam penetrates), the melted titanium flows out from below the titanium briquette 1 and the desired shape cannot be maintained.

  For this reason, the melting depth of the titanium briquette 1 is set to be less than the plate thickness or the diameter of the titanium briquette 1. Usually, it is desirable to dissolve the entire titanium briquette 1 by melting about half of the thickness and diameter and then reversing or rotating to dissolve the remaining half.

  Since the size (width and length) of the titanium briquette 1 is limited, when a large titanium lump 2 is obtained, a plurality of titanium briquettes 1 may be arranged and melt-bonded by an electron beam. Moreover, it is preferable that the air removal treatment from the air gap 1d and the titanium briquette 1 dissolution treatment (including dissolution after inversion) by an electron beam are continuously performed under reduced pressure.

5. Titanium slab 3
Next, a titanium slab 3 and a titanium plate 4a using the titanium block 2 according to the present invention will be described.

  As shown in FIG. 4 or FIG. 5, the titanium slab 3 is used for containers (packing materials) 4 and 40 in which the titanium blocks 2 and 20 obtained above are made of titanium plate materials 4a and 40a having the same kind of chemical composition. It fills and welds all the joints of the packing materials 4 and 40, and forms the welding parts 5 and 50. FIG. The titanium slab 3 is also called a titanium billet or titanium bloom depending on its size and shape, and indicates a material for hot working (intermediate product).

  The titanium slab 3 according to the present invention has a vacuum inside of the titanium plate material 4a and stores the titanium block 2 according to the present invention.

  As shown in FIG. 4, the titanium slab 3 according to the present invention is a titanium slab including a packing material 4 formed of a titanium plate 4 a and a titanium block 2 filled in the packing material 4. The internal pressure of the material 4 is 10 Pa or less in absolute pressure, and the titanium plate material 4 a is a processing material having the same kind of chemical composition as the titanium block 2. As described above, the titanium block 2 is often manufactured so as to satisfy the chemical composition range defined in various standards. The chemical composition of the packing material 4 is preferably in the same chemical composition range as the standard required for the titanium block 2. That is, the same kind means that the packing material 4 and the titanium block 2 are within the same chemical composition range.

  The titanium plate material 4a that forms the packing material 4 will be described.

  The titanium plate 4a is a titanium plate or a titanium tube made by hot or cold plastic working such as rolling, extruding, drawing, or forging. Since the titanium plate 4a is plastically processed, there is an advantage that the surface is smooth and the structure is fine (crystal grains are small).

(5-1) Thickness When the packaging material 4 is a rectangular parallelepiped, the thickness of the titanium plate material 4a varies depending on the size of the packaging material 4 to be produced, but is desirably 0.5 mm or more and 30 mm or less. As the packing material 4 is larger, strength and rigidity are required, so a thicker titanium plate 4a is used.

  If it is less than 0.5 mm, the packaging material 4 may be deformed at the time of heating before hot working or may break at the initial stage of hot working, which is not preferable. If it is thicker than 30 mm, the proportion of the titanium plate material 4a in the thickness of the titanium slab 3 is increased, and the filling amount of the titanium lump 2 is reduced. Therefore, the amount of processing of the titanium lump 2 is small, and the production efficiency is inferior. The thickness of the titanium plate 4a is preferably thin for cost reduction, and may be 20 mm or less, 10 mm, or 5 mm or less. The thickness may be 1 mm or more, 2 mm or more, or 3 mm or more in order to reliably prevent breakage at the initial stage of hot working.

  Furthermore, the thickness of the titanium plate 4a is desirably 3% or more and 25% or less of the thickness of the titanium slab 3. If the thickness of the titanium plate 4a is less than 3% of the thickness of the titanium slab 3, it will be difficult to hold the titanium block 2, and it will be greatly deformed during heating before hot working, or the welded part 5 of the packing 4 will It breaks.

  On the other hand, if the thickness of the titanium plate material 4a is greater than 25% of the thickness of the titanium slab 3, there is no particular problem in manufacturing, but the proportion of the titanium plate material 4a in the thickness of the titanium slab 3 increases. Since the filling amount of the lump 2 is reduced, the amount of processing of the titanium lump 2 is small, and the production efficiency is inferior.

  The same applies to the case where the packing material 4 is a tube. The thickness of the titanium plate 4a varies depending on the size of the packing material 4 to be produced, but the thickness of the tube is preferably 0.5 mm or more and 30 mm or less. Further, as in the case of the rectangular parallelepiped, the thickness of the titanium plate member 4a is desirably 3% or more and 25% or less of the diameter of the titanium slab 3. Moreover, as shown in FIG. 5, the inside of the packing material 40 produced by bending the titanium plate material 40a into a hollow tube is filled with the titanium lump 2, and the end of the titanium plate material 40a is welded to form the welded portion 50. The titanium slab 30 may be used.

(5-2) Chemical composition The packing material 4 needs to be the same chemical composition as the titanium block 2. Here, having the same chemical composition means specifically belonging to the same standard of JIS. For example, when the chemical composition of the titanium block 2 belongs to JIS class 1, the packing material 4 also has a chemical composition belonging to class JIS 1. Here, the standard calculated | required by the titanium lump 2 can be confirmed with the document at the time of sale or manufacture. This standard can also be confirmed from the display on the surface of the titanium block 2. As necessary, within ± 30%, within ± 20%, within ± 15%, within ± 10%, within ± 8%, within ± 5%, or ± 3% from the chemical composition (actual value) of titanium block 2 It may be within.

  Thus, by making the chemical composition of the packing material 4 the same type of chemical composition as the titanium block 2, the surface layer and the inside of the titanium slab after processing can have the same chemical composition, and the titanium block as it is Can be handled.

(5-3) Size of crystal grains of packing material 4 The titanium plate material 4a can be adjusted by subjecting it to an appropriate plastic working and heat treatment. It is desirable that the average crystal grain of the titanium plate 4a used for the packing material 4 is 500 μm or less in terms of equivalent circle diameter. Thereby, when the titanium slab 3 is hot-worked, it is possible to suppress surface defects generated due to the difference in crystal orientation of coarse crystals.

  The lower limit of the equivalent circle diameter of the average crystal grains is not particularly defined, but in order to make the crystal grain diameter extremely small with the titanium plate material 4a, it is necessary to increase the processing ratio at the time of plastic processing. Since the thickness of the titanium plate member 4a that can be used as a limit is limited, it is preferably 10 μm or more, and more preferably greater than 15 μm.

  The target crystal grains are α-phase crystal grains in the case of industrial pure titanium and α-type titanium alloys, and β-phase crystal grains in the case of β-type titanium alloys. In the case of an α + β two-phase titanium alloy, it is an α phase texture (α colony). An α colony is an aggregate of α crystal grains having the same crystal orientation.

  The average crystal grains of industrial pure titanium, α-type titanium alloy and β-type titanium alloy are photographed by observing the structure of the cross section including the thickness direction of the titanium plate material 4a constituting the packing material 4 with an optical microscope, From the structure photograph, the average crystal grain of the surface layer (region from the surface to a depth of 0.3 mm) of the titanium plate 4a is obtained by a cutting method in accordance with JIS G 0551 (2005).

  The average crystal grain size (α colony size) of the α + β two-phase titanium alloy is determined by the following method using EBSD (Electron Backscatter Diffraction).

  First, a test piece having a cross section including the plate thickness direction of the packaging material 4 made of the titanium plate material 4a as an observation surface is collected, and then the surface layer of the observation surface of the test piece (region from the surface to a depth of 0.3 mm). With a rectangular area of 2.4 mm in length and 1.8 mm in width as the field of view, measurement is performed using EBSD at a measurement interval of 2.3 μm and an acceleration voltage of 15 kV. From the obtained measurement results, a PQ (pattern quality) map and a phase map are created by Kikuchi pattern analysis, and an α phase is extracted. The Kikuchi pattern analysis is performed only on the α phase with the β phase excluded. Next, α colonies are determined by setting the angle difference between the crystal orientations of adjacent EBSD measurement points to 15 ° or less, the area of each α colony is obtained from the number of measurement points of the α colonies, and the equivalent circle diameter is calculated.

  Next, the titanium slab 3 will be described.

(5-4) Shape The shape of the titanium slab 3 is not limited, but is determined by the shape of the titanium mass to be produced. When manufacturing a titanium thin plate, the titanium slab 3 has a rectangular parallelepiped shape (slab). The thickness, width and length of the titanium slab 3 are determined by the thickness, width and length of the product, the production amount (weight), and the like.

  When manufacturing a titanium round bar, a wire, or an extruded shape, the titanium slab 3 has a polygonal columnar shape (billet) such as a cylindrical shape or an octagonal column. The size (diameter, length) is determined by the product thickness, width and length, production volume (weight), and the like.

(5-5) Inside The titanium slab 3 is filled with the titanium block 2. One or more titanium ingots 2 can be filled. There is a gap 6 between the titanium block 2 and the packing material 4 or between the titanium blocks 2. If there is air in the gap 6, the filled titanium lump 2 is oxidized or nitrided when heated before hot working, and the titanium material obtained after the work becomes brittle, so that necessary materials are obtained. Characteristics cannot be obtained.

  Further, when filled with an inert gas such as Ar gas, the oxidation or nitridation of the titanium block 2 or the packing body 6 can be suppressed, but the Ar gas thermally expands during heating to expand the packing material 4 and thereby the titanium slab. 3 is deformed and cannot be hot worked.

  For the above reasons, the gap between the titanium block 2 and the packing material 4 or between the titanium blocks 2 must be reduced as much as possible. Specifically, the absolute pressure is preferably 10 Pa or less, and more preferably 1 Pa or less.

If the internal pressure of the packaging material 4 is greater than 10 Pa, the titanium lump 2 and the packaging material 4 are oxidized or nitrided by the remaining air. The lower limit is not particularly limited, but in order to extremely reduce the internal pressure, the manufacturing cost is increased by improving the air tightness of the apparatus or increasing the vacuum exhaust equipment. Therefore, the lower limit of the internal pressure is 1 × 10. ^-3 Pa is desirable.

  In addition, the internal pressure of the produced titanium slab 3 can be measured as follows. That is, a hole is made in the titanium slab 3 in water or in a vacuum chamber, and the volume of the gas (air) remaining inside is collected and measured, or the volume is determined based on the change in the degree of vacuum. Can be calculated. Further, the volume of the voids in the titanium slab 3 can also be grasped by collecting the water that has entered the interior and obtaining the volume. By this method, it can be confirmed that at least the internal pressure of the titanium slab 3 is 10 Pa or less.

(5-6) Depressurization Method Next, a method for depressurizing the inside of the packing material 4 and maintaining a vacuum will be described.

  The packing material 4 is sealed by filling the titanium block 2 and then reducing the pressure so as to be equal to or lower than a predetermined internal pressure. Alternatively, the titanium plate members 4a may be partially joined and then depressurized and sealed. By sealing, air does not enter and the internal titanium lump 2 and the packing material 4 are not oxidized during heating before hot working.

  The sealing method is not particularly limited, but it is preferable to seal the titanium plate members 4a by welding. In this case, the welded portion 5 is formed by welding all the joints of the titanium plate 4a, that is, performing all-around welding. The method for welding the titanium plate 4a is not particularly limited, such as arc welding such as TIG welding or MIG welding, electron beam welding, or laser welding.

  The welding is performed under reduced pressure or in an inert gas atmosphere so that the inner surfaces of the titanium block 2 and the packing material 4 are not oxidized or nitrided. When welding the joint of the titanium plate material 4a at the end, it is desirable to place the packing material 4 in a container (chamber) under reduced pressure and perform welding to keep the inside of the packing material 4 in a reduced pressure state.

  In addition, after providing piping in a part of the packing material 4 and welding the entire circumference in an inert gas atmosphere, the pressure is reduced to a predetermined internal pressure through the piping, and the piping is sealed by crimping etc. The inside of the material 4 may be in a reduced pressure state. In this case, the piping may be installed at a position that does not cause a problem during the hot processing in the subsequent process, for example, at the rear end face.

(5-7) Processing Titanium lump 2 and titanium slab 3 thinner or thinner than the conventional ones obtained as described above are hot processed or cold processed into a desired shape. The processing method varies depending on the shape of the titanium slab, but since each is thin or thin, it can be easily processed to a desired size.

  When manufacturing a titanium plate, the rectangular parallelepiped (slab) titanium block 2 or titanium slab 3 is heated and hot-rolled to obtain a titanium plate. As needed, after removing an oxide layer by pickling etc. like a conventional process, you may cold-roll and process further.

  When manufacturing titanium round bars and wire rods, the titanium ingot 2 or titanium slab 3 having a cylindrical or polygonal column shape is heated and subjected to hot forging, hot rolling or hot extrusion to obtain titanium round bars or wire rods. . Further, if necessary, after removing the oxide layer by pickling or the like, cold rolling or the like may be carried out to make it finer as in the conventional process. In the case of producing a titanium extrusion mold, a cylindrical or polygonal columnar titanium lump 2 or a titanium slab 3 is heated and subjected to hot extrusion to obtain titanium sections having various cross-sectional shapes.

  In the case where the titanium block 2 is used, there is a case where a bald defect is generated on the surface of a plate, a round bar, or a profile after hot working. In this case, surface defects are removed by cutting, pickling or the like.

  When the titanium slab 3 is used, the surface of the plate, the round bar, and the profile after hot working is good, and it is not necessary to care for the surface.

  Next, examples of the present invention will be described.

  As a raw material titanium source, sponge titanium produced by a crawl method (particle size = 0.25 mm to 19 mm), oxygen content 0.03%, iron content 0.02%, nitrogen content 0.002%, A carbon content of 0.001% and a hydrogen content of 0.001% were used. Also, as titanium scrap, JIS Class 1 (oxygen content 0.04%, iron content 0.03%, nitrogen content 0.001%, carbon content 0.003%, hydrogen content 0.007%) A thin plate cut into 20 to 30 mm square was partially used (see Nos. 11 and 12 in Table 1).

As auxiliary materials, titanium oxide powder, electrolytic iron, Pd powder grain, Al grain, Al-V alloy grain, Sn grain, Zr grain, Mo powder, Ta powder, Nb powder, Si powder, Cr grain, Co grain, Ni Grains, Ru powder, Mm (Misch metal) powder, FeN powder, C powder, and TiB ₂ powder were appropriately used according to the target chemical composition of the titanium mass. The Al-V alloy grains are alloys having an Al content of 30% and a V content of 70%. For Mm, a mixture mainly composed of La (lanthanum), Ce (cerium), and Nd (neodymium) was used.

  Sponge titanium, titanium scrap, and auxiliary materials were put into a stainless steel mixing container, and the raw materials were mixed by rotating the mixing container up and down. A predetermined amount of the mixed raw material was put into a square mold and compression-molded to produce a rectangular parallelepiped titanium briquette. At this time, the porosity determined from the size and weight of the titanium briquette was 28 to 45%.

  The obtained titanium briquette was put in a vacuum chamber, and the upper surface of the titanium briquette was melted by 2 to 3 mm more than half the thickness of the titanium briquette by an electron beam. For the amount (thickness) to be dissolved, the relationship between the output of the electron beam and the thickness that can be dissolved was obtained in advance, and the output of the electron beam was obtained from the required thickness from the result. After solidifying and cooling the upper surface of the titanium briquette, the titanium briquette was inverted and the back surface was similarly dissolved.

  In this way, the entire titanium briquette was melted and solidified, and rectangular parallelepiped titanium ingots having a width of 300 mm and a length of 1200 mm were produced.

  As a comparative example, a titanium lump that melts only the vicinity of the surface of the titanium lump but does not dissolve the raw material inside was also manufactured (see Nos. 25 and 26 in Table 1). In any example, the thickness of the dissolved surface layer was 4-8 mm on each side.

  The obtained titanium ingot was partly cut and subjected to component analysis to evaluate its homogeneity. The remaining titanium ingot was hot-rolled to obtain a rolled plate having a thickness of 3.5 to 8.0 mm.

  As a conventional example, a titanium ingot was obtained in an EB melting furnace having cold hearth. That is, a titanium ingot was obtained by putting sponge titanium, titanium oxide, electrolytic iron, and Al particles as raw materials into cold hearth, and irradiating the raw materials with an electron beam and injecting molten titanium into a 250 mm thick mold. The initial dissolution was started at a dissolution rate of 0.35 ton / h, the dissolution rate was gradually increased, and the solution was dissolved at 0.75 ton / h in the stationary part. Thereafter, the dissolution rate was gradually reduced to 0.2 ton / h at the end of dissolution, and then the dissolution was finished to obtain a titanium ingot having a length of 1200 mm.

The crystal grain size at the center of the titanium block was measured visually or using a metal microscope. In addition, the component analysis of the titanium block was performed by taking a required amount of a sample for analysis from a predetermined position of the titanium block and using any of the analysis methods listed below.
JIS H 1612 (1993) Method for determination of nitrogen in titanium and titanium alloys
JIS H 1614 (1995) Determination of iron in titanium and titanium alloys
JIS H 1617 (1995) Determination of carbon in titanium and titanium alloys
JIS H 1619 (2012) Titanium and titanium alloys-Determination of hydrogen
JIS H 1620 (1995) Determination of oxygen in titanium and titanium alloys
JIS H 1621 (1992) Determination of palladium in titanium alloys
JIS H 1622 (1998) Titanium alloy-aluminum determination method
JIS H 1624 (2005) Titanium alloy-vanadium determination method
JIS H 1625 (2005) Titanium alloy-Determination of lanthanum, cerium, praseodymium and neodymium
JIS H 1630 (1995) Titanium emission spectroscopy method
JIS H 1631 (2008) Titanium alloy-X-ray fluorescence analysis method
JIS H 1632 (2014) ICP emission spectroscopic analysis method for titanium

  As samples for analysis, there are two locations (end region) 50 mm from the front and rear ends of the titanium block 2 in the longitudinal direction, and the central position of each equal length by dividing it into three equal parts. Samples were collected from a total of three locations. In the cross section of the titanium lump 2, in the case of a rectangular parallelepiped (slab) titanium lump 2, the center of the cross section is symmetrical in the case of a columnar (ingot) titanium lump in the surface layer on the front and back surfaces at the center in the width direction. Collected from two surface layers. Further, at a position of 50 mm from the front end and the rear end in the longitudinal direction, the sample was also taken from the center of the thickness center / diameter direction. In this way, samples for analysis were collected from a total of 12 locations (positions marked with ● in FIG. 6) and analyzed, and the uniformity of the chemical composition was evaluated as follows.

When the difference ΔC between the maximum value C _MAX and the minimum value C _MIN of the content of each element was less than 0.2 C _MIN or less than 0.04%, it was evaluated that the uniformity was good. For example, when the minimum value of the measured value of O is 0.04% and the maximum value is 0.05%, the difference ΔC (= 0.01%) is less than 0.04%, so the uniformity is good. It was evaluated that. Further, when the minimum value of the measured value of O is 0.30% and the maximum value is 0.32%, the difference ΔC (= 0.02%) is less than 0.2C _MIN (= 0.060%). Therefore, it was evaluated that the uniformity was good.

  In addition, at a position of 50 mm from the front end and the rear end in the longitudinal direction, the crystal grain size at the center of the thickness was measured visually or using a metal microscope, and the average value was obtained. The remaining titanium ingot was hot-rolled into a plate having a thickness of 3.5 mm to 8 mm.

  Table 2 shows the production conditions of the titanium ingot in Example 1, Table 3 shows the manufactured titanium ingot, and Table 4 shows the titanium material (rolled plate) produced by rolling the titanium ingot.

  As shown in Tables 2 to 4, No. In Nos. 1 to 8, titanium ingots were produced with various thicknesses by changing the thickness and porosity of the titanium briquette.

  No. No. 1 could not be rolled because a thin titanium block having a thickness of 5.7 mm was obtained when the thickness of the titanium briquette was as thin as 8 mm, but some corners of the titanium briquette were missing.

  No. of other thicknesses 2-8, the chemical composition is homogeneous, the crystal grain size at the center of the thickness of the titanium ingot is as small as 0.8-7.8 mm, rolling can be performed without any problem, and part of the surface of the rolled plate Although surface flaws occurred, they were generally good. The surface flaws that occurred in part could be removed by partial care.

  No. Nos. 8 to 10 are cases in which rolled sheets of JIS type 1, JIS type 3 and JIS type 4 are produced. Nos. 11 and 12 are cases where some or all of JIS type 1 titanium scrap is used to produce JIS type 2 and JIS type 3 rolled sheets.

  In any of these cases, a titanium ingot having a uniform component with little fluctuation in the component and a small crystal grain size at the center was obtained, and the subsequent rolling could be performed without any problem. Although surface flaws occurred on a part of the surface of the rolled plate, it was generally good.

  No. 13-24 is the case where various metal elements other than Fe and Fe are added as auxiliary materials. In any of these cases, a titanium ingot having a uniform and small central crystal grain size can be obtained, and the subsequent rolling can be performed without any problem, and a surface flaw is formed on a part of the surface of the rolled plate. Although it occurred, it was generally good.

  No. which is a comparative example. In Nos. 25 and 26, a titanium lump was produced by dissolving the vicinity of the surface layer of the titanium briquette and leaving the inside without dissolving the raw material (sponge titanium, auxiliary material). Since the thickness central portions of these titanium ingots are not melted, the two central portions at positions (end regions) 50 mm from the front end and the rear end in the longitudinal direction remain titanium briquettes. For this reason, the analysis of the central part and the measurement of the crystal grain size are not possible, and therefore omitted. That is, in the analysis, the uniformity of the chemical composition was evaluated from 10 points collected from the surface layer part of the dissolved titanium block.

  In these titanium ingots, additive elements other than titanium such as oxygen and Fe greatly fluctuated depending on the position of the titanium ingot, resulting in a heterogeneous ingot. Furthermore, when this ingot was rolled, deformation resistance at high temperatures was greatly different due to the inhomogeneity of this component, and many large surface cracks were generated. For this reason, it could not be used as a product.

  In addition, No. 1-No. In all 26 comparative examples and inventive examples, the titanium content was 70% or more. Carbon, nitrogen, and hydrogen contained as impurities in sponge titanium and titanium scrap are included in all comparative examples and examples of the present invention.

  It is a conventional example, No. 27 is a result of melting industrial pure titanium (JIS type 2) by the conventional method. Since the slab is as large as 250 mm, the variation of the Fe component is large due to solidification segregation, and the crystal grain at the center of the thickness is also as large as 13 mm. . Further, the thin plate after rolling frequently had a bald surface flaw. No. No. 28 is the result of melting the Ti-5Al-1Fe alloy. Since the slab was as large as 250 mm, the variation in the Fe component was large due to solidification segregation, and the crystal grain at the center of the thickness was also as large as 12 mm. Further, due to variations in the volatilization amount of Al, fluctuations in the Al component are also large. In addition, the thin plate after rolling frequently had shaved surface defects.

  No. of Example 1 A titanium slab was manufactured using a titanium block manufactured in the same manner as in No. 4 and having a thickness of 35 mm, a width of 300 mm, and a length of 400 mm.

As the titanium packing material, the same JIS 2 seed material as that of the titanium lump having a thickness of 1 to 20 mm was used.
When rolling the titanium slab, a pipe with a valve was fixed by TIG welding to one piece of the titanium packing material that would be the side of the container that was not in contact with the rolling roll. Keep piping valves closed. After 5 pieces of titanium packing material including the titanium packing material welded to the pipe were temporarily assembled into a container, the titanium lump was stored here and covered with the remaining titanium packing material. The temporarily assembled package was placed in a vacuum chamber and decompressed (vacuum) until a predetermined pressure was reached, and then the seam of the packaging material was welded with an entire circumference electron beam to produce a titanium slab (Table 5). No. 2, 3, 5). A vacuum gauge was installed in the pipe on the side of the manufactured titanium slab, and the internal pressure was measured by opening the valve. After the measurement, this pipe was sealed between the titanium slab and the valve, and the valve was cut and removed.

  In addition, after assembling the titanium slab by TIG welding, from the exhaust pipe provided in the titanium packing material, after reducing the pressure (vacuum) until the inside of the titanium slab reaches a predetermined pressure, by sealing the exhaust pipe, The internal pressure of the titanium slab was adjusted.

  These titanium slabs having a thickness of 37 to 75 mm were rolled to produce rolled plates having a thickness of 4.0 to 5.5 mm.

  The results of Example 2 are shown together with the test conditions in Table 5.

  As shown in Table 5, the internal pressure of the titanium slab was set to 10 Pa or less. In 1-3, it rolled without a problem and the surface of the obtained rolled sheet was also favorable.

  No. 1 in which the internal pressure of the titanium slab was 12 Pa. In No. 4, although rolling was possible without any problem, the obtained rolled sheet was partially broken into two pieces and peeling occurred. When the part where peeling occurred was observed, it was found that the surfaces of the titanium lump and the titanium packing material were oxidized, and the two materials were not pressure-bonded.

  Similarly, No. 1 in Example 1 was used. A titanium slab was manufactured using a titanium block manufactured in the same manner as in No. 14.

  As the titanium packing material, the same Ti-5Al-1Fe material (numbers are mass%) as the titanium block having a thickness of 10 mm was used. After 5 pieces of titanium packing material were temporarily assembled into a container, the titanium block was stored here and covered with the remaining titanium packing material.

  The temporarily assembled package was put in a vacuum chamber and decompressed (vacuum) until a predetermined pressure was reached, and then the seam of the packaging material was welded with an electron beam all around to produce a titanium slab (No. 5). ).

  The titanium slab was rolled to produce a rolled plate having a thickness of 5.0 mm. Rolling was possible without problems, and the surface of the obtained rolled plate was also good.

  As a titanium source of the raw material, sponge titanium produced by a crawl method (particle size = 0.25 mm or more and 19 mm or less), oxygen content 0.04%, iron content 0.03%, nitrogen content 0.003%, A carbon content of 0.003% and a hydrogen content of 0.001% were used. Moreover, as titanium scrap, JIS Class 1 (oxygen content 0.04%, iron content 0.03%, nitrogen content 0.003%, carbon content 0.004%, hydrogen content 0.003%) A thin plate cut into 20 to 30 mm square was partially used (see Nos. 10 and 11 in Table 3).

As auxiliary materials, titanium oxide powder, electrolytic iron, Pd powder grain, Al grain, Al-V alloy grain, Sn grain, Zr grain, Mo powder, Ta powder, Nb powder, Si powder, Cr grain, Co grain, Ni Grains, Ru powder, Mm (Misch metal) powder, FeN powder, C powder, and TiB ₂ powder were appropriately used according to the target component of the titanium lump. The Al-V alloy grains are alloys having an Al content of 30% and a V content of 70%.

  Sponge titanium, titanium scrap, and auxiliary materials were put into a stainless steel mixing container, and the raw materials were mixed by rotating the mixing container up and down. A predetermined amount of the mixed raw material was put into a cylindrical mold and compression molded to produce three cylindrical titanium briquettes (length: 300 mm). At this time, the porosity determined from the size and weight of the titanium briquette was 28 to 40%.

  Three of the obtained titanium briquettes were arranged in the longitudinal direction and placed in a vacuum chamber, and the peripheral surface of the titanium briquette was dissolved by 2 to 3 mm more than half the diameter of the titanium briquette by an electron beam. The amount (diameter) to be melted was obtained in advance from the relationship between the output of the electron beam and the thickness that can be melted, and the output of the electron beam was determined from the required thickness. While rotating the titanium briquette, the entire peripheral surface was melted and solidified.

  In this way, the entire titanium briquette was melted and solidified to produce a cylindrical titanium block having a length of 900 mm and a diameter of 9 to 78 mm. The uniformity of chemical composition and the crystal grain size were evaluated in the same manner as in Example 1.

  As a conventional example, a titanium ingot was obtained in an EB melting furnace having cold hearth. That is, sponge titanium, titanium oxide, electrolytic iron, and Al particles were put into cold hearth as raw materials, and injected into a molten titanium mold having a diameter of 600 mm by irradiating the raw material with an electron beam. The initial dissolution was started at a dissolution rate of 0.5 ton / h, and the dissolution rate was gradually increased to dissolve at 0.85 ton / h in the stationary part. Thereafter, the dissolution rate was gradually reduced to 0.3 ton / h at the end of dissolution, and then the dissolution was terminated to obtain a titanium ingot having a length of 900 mm. This titanium ingot was sampled for analysis and microstructure observation, then forged to φ100 mm, and further rolled into a φ30 mm round bar.

  Table 6 shows the production conditions of the titanium ingot in Example 3, Table 7 shows the manufactured titanium ingot, and Table 8 shows the titanium material (round bar) produced by rolling the titanium ingot.

  As shown in Tables 6 to 8, as a comparative example, No. No. 22 also produced a titanium ingot that melts only the vicinity of the surface of the titanium ingot and does not dissolve the raw material inside.

  The obtained titanium mass was sampled for analysis in the same manner as in Example 1 and subjected to chemical composition analysis, and its homogeneity was evaluated by the same method as in Example 1. Further, the crystal grain size of the central part of the cross section perpendicular to the longitudinal direction at the central part in the longitudinal direction was measured visually or using a metal microscope. The remaining titanium ingot was hot rolled into a round bar with a diameter of 8 mm to 18 mm.

  No. in Tables 6-8. Nos. 1 to 6 are cases where titanium ingots with various diameters were manufactured by changing the diameter and porosity of the titanium briquette. When the diameter of the titanium briquette was as small as 11 mm, a thin titanium lump with a diameter of 9 mm was obtained, but it could not be rolled because it was broken at a part of the titanium briquette (No. 1). Titanium ingots with other diameters could be rolled without problems, and good quality round bars were obtained (Nos. 2 to 6).

  No. Nos. 7 to 9 are cases where titanium ingots of JIS type 1, JIS type 3 and JIS type 4 were produced. 10 and 11 are cases in which some or all of JIS type 1 titanium scrap is used to produce JIS type 2 and JIS type 3 rolled sheets. In each case, a titanium ingot having a uniform chemical composition with little variation in the chemical composition and a small center crystal grain size was obtained, and a good quality round bar was obtained without any subsequent rolling.

  No. 12 to 21 are cases where various metal elements other than Fe and Fe are added as auxiliary materials. In each case, a titanium block having a uniform and small central crystal grain size with little variation in the components was obtained, and the subsequent rolling could be performed without any problem, and a high-quality round bar could be produced.

  No. which is a comparative example. In No. 22, a titanium block having a diameter of 44 mm was produced by dissolving the vicinity of the surface layer of the titanium briquette and leaving the inside without dissolving the raw material (sponge titanium, auxiliary raw material). Since the thickness central part of this titanium lump is not melted, the two central parts at positions (end regions) 50 mm from the front end and rear end in the longitudinal direction remain titanium briquettes. For this reason, the analysis of the central part and the measurement of the crystal grain size are not possible, and therefore omitted. That is, in the analysis, the uniformity of the chemical composition was evaluated from 10 points collected from the surface layer part of the dissolved titanium block.

  When the chemical composition of the titanium ingot was analyzed, oxygen and Fe added as auxiliary materials varied greatly depending on the position of the titanium ingot, resulting in a heterogeneous ingot. Further, when the ingot was rolled, the deformation resistance at high temperature was greatly different with the inhomogeneity of the chemical composition, and many large surface cracks were generated. For this reason, it could not be used as a product.

  In addition, No. 1-No. In all 22 comparative examples and inventive examples, the titanium content was 70% or more. Carbon, nitrogen, and hydrogen contained as impurities in sponge titanium and titanium scrap are included in all comparative examples and examples of the present invention.

  It is a conventional example, No. No. 23 is a result of melting industrial pure titanium (JIS type 2) by a conventional method. Since the ingot diameter is as large as 600 mm, the dispersion of Fe components is large due to solidification segregation, and the crystal grains at the center of the thickness are also as large as 14 mm. It was. Moreover, since surface cracks frequently occurred during forging, the portion had to be removed by cutting, and the production yield was greatly reduced. No. No. 24 is a result of melting a Ti-6Al-4V alloy by a conventional method. Since the ingot diameter is as large as 600 mm, the variation of the Fe component is large due to solidification segregation, and the crystal grain at the center of the thickness is also as large as 13 mm. Further, due to variations in the volatilization amount of Al, fluctuations in the Al component are also large. Moreover, since surface cracks frequently occurred during forging, the portion had to be removed by cutting, and the production yield was greatly reduced.

  According to the present invention, thin or thin titanium ingots having various chemical compositions can be manufactured by omitting the conventional melting step and forging step, and the amount of processing in the hot processing of the next step is also reduced. Thus, a titanium mass can be produced. For this reason, the energy which manufacture requires can be reduced. Furthermore, by using a titanium slab, it is possible to omit the cutting and removal of defects generated on the surface of the titanium lump, and the manufacturing yield can be greatly improved and the manufacturing cost can be greatly reduced.

Claims (5)

It is a titanium block with a thickness of 7 to 80 mm,
Chemical composition is mass%,
O: 0.01 to 0.5%
Fe: 0.01 to 5%,
Al: 0 to 8%,
Sn: 0 to 5%
Zr: 0 to 12%,
Mo: 0 to 15%,
Ta: 0 to 2%
V: 0 to 22%
Nb: 0 to 2%,
Si: 0 to 1%,
Cr: 0 to 10%
Cu: 0 to 0.1%,
Co: 0 to 1%,
Ni: 0 to 1%,
Platinum group elements: 0 to 0.5%,
REM: 0-0.2%
B: 0 to 3%
N: 0 to 0.2%,
C: 0 to 2%
H: 0 to 0.013%,
The balance is titanium and impurities,
The difference ΔC between the maximum value C _MAX and the minimum value C _MIN of the measured values of each element is less than 0.2C _MIN or less than 0.04%,
The metal structure is
The circle-equivalent average crystal grain size in the central portion of the titanium lump in the thickness direction is 10 mm or less and half or less of the thickness of the titanium lump.
Titanium lump. A titanium lump having a columnar shape in which a cross section perpendicular to the longitudinal direction is a circle having a diameter of 10 to 80 mm, or a columnar shape that is a polygon of a pentagon or more having a circle equivalent diameter of 10 to 80 mm,
Chemical composition is mass%,
O: 0.01 to 0.5%
Fe: 0.01 to 5%,
Al: 0 to 8%,
Sn: 0 to 5%
Zr: 0 to 12%,
Mo: 0 to 15%,
Ta: 0 to 2%
V: 0 to 22%
Nb: 0 to 2%,
Si: 0 to 1%,
Cr: 0 to 10%
Cu: 0 to 0.1%,
Co: 0 to 1%,
Ni: 0 to 1%,
Platinum group elements: 0 to 0.5%,
REM: 0-0.2%
B: 0 to 3%
N: 0 to 0.2%,
C: 0 to 2%
H: 0 to 0.013%
The balance is titanium and impurities,
The difference ΔC between the maximum value C _MAX and the minimum value C _MIN of the measured values of each element is less than 0.2C _MIN or less than 0.04%,
The metal structure is
In a cross section perpendicular to the longitudinal direction of the titanium block, it has a columnar structure extending in the direction from the surface toward the center, the circle-equivalent average crystal grain size at the center position of the cross section is 10 mm or less, and half or less of the diameter of the cross section Is,
Titanium lump. A packing material having the same chemical composition as the titanium ingot according to claim 1 or 2,
The titanium ingot according to claim 1 or 2 filled in the packing material,
The packing material has an internal pressure of 10 Pa or less,
Titanium slab. A compression molding process for obtaining a titanium briquette by compression molding one or more selected from sponge titanium and titanium scrap and an auxiliary material containing an element necessary for adjusting the chemical composition;
A step of irradiating the surface of the titanium briquette with an electron beam under a reduced pressure of 1 Pa or less to dissolve all of the titanium briquette into a titanium lump,
The manufacturing method of the titanium lump of Claim 1 or 2. In the melting step, an arbitrary surface of the titanium briquette is irradiated with an electron beam, a part of the thickness direction is melted from the surface, and an arbitrary other surface is irradiated with an electron beam, and at least undissolved. A step of dissolving the titanium briquette of
The manufacturing method of the titanium lump of Claim 4.

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